The present invention claims the benefit of Korean Patent Application No. 2000-86338, filed in Korea on Dec. 29, 2000, which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to an identification (ID) mark forming method of an array substrate for liquid crystal display devices.
2. Discussion of the Related Art
Liquid crystal display devices have become popular because of their low power consumption and superior portability. In general, a liquid crystal display device comprises a lower substrate that includes thin film transistors, commonly referred to as an array substrate, and an upper substrate that includes a color filter, commonly referred to as a color filter substrate, and a liquid crystal material disposed between the upper substrate and the lower substrate. The liquid crystal display device makes use of optical anisotropy and polarization properties of the liquid crystal material to display image data (images). Presently, active matrix LCD (AM LCD) devices are one of the most popular means for displaying images because of their high resolution and superiority in displaying moving images.
A plurality of gate lines, which receive scanning signals, and a plurality of data lines, which receive data signals, are disposed on the array substrate to define a plurality of pixel regions. A pixel electrode, which is connected to a thin film transistor, is formed in each pixel region to apply a voltage to the liquid crystal material. On the color filter substrate, a color filter, which includes sub-color filters R, G and B, that corresponds to the pixel region on the array substrate is formed on the color filter substrate. A black matrix is formed on the color filter to intercept light in a region other than the pixel electrode region, thereby preventing light from irradiating the corresponding thin film transistor. The color filter substrate further includes a common electrode that applies a voltage to the liquid crystal material.
The common electrode and the pixel electrode are respectively formed on internal opposing sides of the color filter substrate and the array substrate, respectively, with the liquid crystal material being disposed between the color filter substrate and the array substrate. The liquid crystal cell is completed by forming polarizing films on external sides of the color filter substrate and the array substrate. A light transmittance of the liquid crystal cell can be controlled by application of a voltage to the common electrode and the pixel electrode, thereby images are displayed using a light-shutter effect. When compared with a thin film transistor forming process and a color filter forming process, a liquid crystal cell forming process is simplified because it does not include repeated sub-processing steps. The complete process for forming the liquid crystal cell includes an alignment film forming process, a cell gap forming process, a liquid crystal injection process, a cell cutting process, and an inspection process. In addition way, a titling process that includes a process for making an identification mark on the array substrate is integrated into the forming process of the array substrate, thereby increasing efficiency of the automated processes for fabricating liquid crystal display devices.
FIG. 1 is a flow chart showing an identification mark forming process of an array substrate for a liquid crystal display device according to the related art. In FIG. 1, a first step ST1 forms a glass identification mark on a metal layer during an array element forming process. The glass identification mark is formed on the array substrate during a gate line or a data line forming process, and is read by an Optical Character Reader (OCR) using a reflection or transmission detection method. A panel identification mark for each array cell on the array substrate is subsequently formed during a liquid crystal cell forming process, thereby preventing an increase in the total number of masks required during the array element forming process. A second step ST2 forms the panel identification mark for each array cell during the liquid crystal cell forming method. The panel identification mark is formed after a detection process of the glass identification mark, and is performed between the alignment film forming process and the cell gap forming process. Because the color filter substrate and the array substrate are to be assembled based on the array substrate, an additional identification mark forming process on the color filter substrate is not necessary. Accordingly, since the panel identification mark forming step is dependent upon the detection of the glass identification mark, the glass identification mark forming process effects an efficiency of the total process for fabricating the array substrate of the liquid crystal display device.
FIG. 2 is a plan view illustrating an array substrate of a liquid crystal display device with a glass identification mark on a metal layer according to the related art, and illustrates an example where two array cells are formed on a transparent substrate. In FIG. 2, array cells 12 having a display area I, and a non-display area II are formed on a transparent substrate 1. A panel identification mark 16 is formed on the non-display area II of the array cells 12, and the glass identification mark 14 is formed on a marginal blank portion of the transparent substrate 1. The glass identification mark 14 is formed using a metal layer during the forming process of the gate line (not shown) or the data line (not shown) of the array cells. As shown in an enlarged view of the glass identification mark 14, a set of identification characters 10 is formed in intaglio in the glass identification mark 14. The identification characters 10 are formed by removing a portion of the metal layer in a glass identification mark forming region on the transparent substrate 1. Additional portions of the metal layer remain in a portion 18 to surround the identification characters 10. Accordingly, the glass identification mark 14 can be detected during the detection process by transmission of light through the identification characters 10.
FIG. 3 is a cross-sectional view illustrating a display area I of the array cell, and a glass identification mark forming region, wherein a gate line 20 is formed in the display area I. In FIG. 3, the gate line 20 is formed on the transparent substrate 1, and the glass identification mark 14 is simultaneously formed of a same metal material as a material of the gate line 20 in the glass identification mark forming region xe2x80x9cmxe2x80x9d on the transparent substrate 1. A gate insulating layer 22 is formed on the gate line 20 and the glass identification mark 14, and a passivation layer 24 is formed on the gate insulating layer 22. Since only transparent materials are positioned over and under the identification characters 10, incident light along an xe2x80x9cLxe2x80x9d direction can transmit through the opened identification character portion, thereby the detection of the glass identification mark can be performed. An additional light exposing apparatus is necessary to create the identification characters 10 of the glass identification mark 14. Etching of exposed portions of the identification characters 10 is performed simultaneously with etching of the gate line 20. The etching process may include a wet etching process using a chemical solution or a dry etching process using a plasma gas. The wet etching process is advantageous for its low equipment costs and a high productivity, and the dry etching process is advantageous for its relatively short processing time and suitability for etching a minuscule pattern. In addition, since the dry etching process is performed in a vacuum chamber, the dry etching is far safer than the wet etching process. The wet etching process is generally used where a metal layer is to be etched to overcome a metal residue problem. However, since the wet etching process tends to over-etch patterns, it may decrease the productivity by causing an identification mark detection error that is caused by an over-etching of the identification mark.
Accordingly, the present invention is directed to an array substrate of a liquid crystal display device with identification mark and a identification mark forming method of the array substrate of the liquid crystal display device that substantially obviates one or more of problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide an array substrate for liquid crystal display devices with an identification mark.
Another object of the present invention is to provide an identification mark forming method of the array substrate for liquid crystal display devices having a simplified process.
Another object of the present invention is to provide an identification mark forming method having increased productivity.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, an array substrate for liquid crystal display devices includes a transparent substrate, a plurality of array cells on the transparent substrate, each of the array cells include a display area and a non-display area having a first identification, and a semiconductor layer including a second identification mark.
In another aspect, an identification mark forming method of an array substrate for liquid crystal display devices includes forming at least one array cell on a transparent substrate, the array cell including a gate line, a gate insulating layer, a transparent amorphous silicon layer, an opaque doped amorphous silicon layer, a data line, a display area, and a non-display area, forming a first identification mark on a marginal blank portion of the transparent substrate by etching the transparent amorphous silicon layer and the opaque doped amorphous silicon layer during an array element forming process, detecting the first identification mark, and forming a second identification mark on the non-display area of each of the at least one array cell after detecting the first identification mark.
In another aspect, an identification mark forming method includes forming at least one array cell on a transparent substrate, the array cell including a semiconductor layer, a display area, and a non-display area, forming a first identification mark on a marginal blank portion of the transparent substrate by etching the semiconductor layer, detecting the first identification mark, and forming a second identification mark on the non-display area of each of the at least one array cell after detecting the first identification mark.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.